dvd shrink limits?

hello
I like to know if there is any buffer and read limit with dvd shrink 3.1.5. The highest buffer that I usually get is 128mb with my P4 2.4G ghz 256mb ddr 466 at home and my P4 3.0 ghz 1gb rambus at my businness. I am not to familiar with all of this but is buffer related to RAM? Thank you.